The present invention relates to a digital copier to which an external storing device of the kind using a laser card and other storing media may be affixed.
In a prior art analog copier, image light produced by scanning an original document is directly focused on a photoconductive element by an optical arrangement. Such a copier, therefore, is incapable of storing image data as provided by scanning the document in a certain place, not to speak of protecting the image data for secrecy.
When it comes to a digital copier having a capability of converting image data as provided by scanning an original document into an electrical signal, the electric signal can be stored if use is made of a suitable storing medium. With a digital copier, it has been customary to store graphic data and character data together in a single storing medium by transforming characters into bit images through character codes in the same manner as pictures. In this manner, when pictures and characters are recorded and reproduced mixed with each other, it is a common practice to convert character data into bit images in the same manner as graphic data so that they may be recorded and reproduced together with graphic data. A problem with such a recording and reproducing system is that since the amount of data to accommodated is large, an optical disk and other expensive mass storages have to be used in place of an inexpensive floppy disk and others whose capacity is relatively small (1 to 2 megabits). For example, to store data printed on an original document of format of A3 at 400 dpi inch, a capacity of 32 megabits is needed. While graphic and character data may be stored after being compressed as already proposed, a sufficient degree of compression has not been achieved yet.
On the other hand, when the memory area left unoccupied in an IC (integrated circuit) card, magnetic card, optical file or like storing medium becomes scanty, it is usually replaced with another wasting the remaining memory area. This is undesirable from the viewpoint of effective use of a storing medium.
Further, in a recording medium of the kind described, it is a common practice to assign memory addresses to part of the memory area so as to record the remaining amount of capacity. However, the remaining amount of capacity cannot be seen without resorting to an exclusive reading device, i.e., the storing medium cannot display the remaining capacity for itself.
In an optical disk system and others having a capacity great enough to accommodate a considerable amount of data, an arrangement is made such that image data read are stored with headings added thereto on a page-by-page basis for the purpose of facilitating searches which may be desired in the future. This brings about another drawback that, for example, image data continuously read from a series of documents which are fed by a document feeder cannot be sequentially outputted unless one enters a particular output order on an operation board by troublesome manipulation.